/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package dwz.common.util.time;

import java.util.Calendar;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

/**
 * 格式化日期到字符串工具，线程安全
 * <p>
 * Date and time formatting utilities and constants.
 * </p>
 * 
 * <p>
 * Formatting is performed using the
 * {@link org.apache.commons.lang.time.FastDateFormat} class.
 * </p>
 * 
 * @author Apache Software Foundation
 * @author Apache Ant - DateUtils
 * @author <a href="mailto:sbailliez@apache.org">Stephane Bailliez</a>
 * @author <a href="mailto:stefan.bodewig@epost.de">Stefan Bodewig</a>
 * @author <a href="mailto:ggregory@seagullsw.com">Gary Gregory</a>
 * @since 2.0
 * @version $Id: DateFormatUtils.java 905636 2010-02-02 14:03:32Z niallp $
 */
public class DateFormatUtils {

	/**
	 * ISO8601 formatter for date-time without time zone. The format used is
	 * <tt>yyyy-MM-dd'T'HH:mm:ss</tt>.
	 */
	public static final FastDateFormat ISO_DATETIME_FORMAT = FastDateFormat
			.getInstance("yyyy-MM-dd'T'HH:mm:ss");

	/**
	 * ISO8601 formatter for date-time with time zone. The format used is
	 * <tt>yyyy-MM-dd'T'HH:mm:ssZZ</tt>.
	 */
	public static final FastDateFormat ISO_DATETIME_TIME_ZONE_FORMAT = FastDateFormat
			.getInstance("yyyy-MM-dd'T'HH:mm:ssZZ");

	/**
	 * ISO8601 formatter for date without time zone. The format used is
	 * <tt>yyyy-MM-dd</tt>.
	 */
	public static final FastDateFormat ISO_DATE_FORMAT = FastDateFormat
			.getInstance("yyyy-MM-dd");

	/**
	 * ISO8601-like formatter for date with time zone. The format used is
	 * <tt>yyyy-MM-ddZZ</tt>. This pattern does not comply with the formal
	 * ISO8601 specification as the standard does not allow a time zone without
	 * a time.
	 */
	public static final FastDateFormat ISO_DATE_TIME_ZONE_FORMAT = FastDateFormat
			.getInstance("yyyy-MM-ddZZ");

	/**
	 * ISO8601 formatter for time without time zone. The format used is
	 * <tt>'T'HH:mm:ss</tt>.
	 */
	public static final FastDateFormat ISO_TIME_FORMAT = FastDateFormat
			.getInstance("'T'HH:mm:ss");

	/**
	 * ISO8601 formatter for time with time zone. The format used is
	 * <tt>'T'HH:mm:ssZZ</tt>.
	 */
	public static final FastDateFormat ISO_TIME_TIME_ZONE_FORMAT = FastDateFormat
			.getInstance("'T'HH:mm:ssZZ");

	/**
	 * ISO8601-like formatter for time without time zone. The format used is
	 * <tt>HH:mm:ss</tt>. This pattern does not comply with the formal
	 * ISO8601 specification as the standard requires the 'T' prefix for times.
	 */
	public static final FastDateFormat ISO_TIME_NO_T_FORMAT = FastDateFormat
			.getInstance("HH:mm:ss");

	/**
	 * ISO8601-like formatter for time with time zone. The format used is
	 * <tt>HH:mm:ssZZ</tt>. This pattern does not comply with the formal
	 * ISO8601 specification as the standard requires the 'T' prefix for times.
	 */
	public static final FastDateFormat ISO_TIME_NO_T_TIME_ZONE_FORMAT = FastDateFormat
			.getInstance("HH:mm:ssZZ");

	/**
	 * SMTP (and probably other) date headers. The format used is
	 * <tt>EEE, dd MMM yyyy HH:mm:ss Z</tt> in US locale.
	 */
	public static final FastDateFormat SMTP_DATETIME_FORMAT = FastDateFormat
			.getInstance("EEE, dd MMM yyyy HH:mm:ss Z", Locale.US);

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * DateFormatUtils instances should NOT be constructed in standard
	 * programming.
	 * </p>
	 * 
	 * <p>
	 * This constructor is public to permit tools that require a JavaBean
	 * instance to operate.
	 * </p>
	 */
	public DateFormatUtils() {
		super();
	}

	/**
	 * <p>
	 * Formats a date/time into a specific pattern using the UTC time zone.
	 * </p>
	 * 
	 * @param millis
	 *            the date to format expressed in milliseconds
	 * @param pattern
	 *            the pattern to use to format the date
	 * @return the formatted date
	 */
	public static String formatUTC(long millis, String pattern) {
		return format(new Date(millis), pattern, DateUtils.UTC_TIME_ZONE, null);
	}

	/**
	 * <p>
	 * Formats a date/time into a specific pattern using the UTC time zone.
	 * </p>
	 * 
	 * @param date
	 *            the date to format
	 * @param pattern
	 *            the pattern to use to format the date
	 * @return the formatted date
	 */
	public static String formatUTC(Date date, String pattern) {
		return format(date, pattern, DateUtils.UTC_TIME_ZONE, null);
	}

	/**
	 * <p>
	 * Formats a date/time into a specific pattern using the UTC time zone.
	 * </p>
	 * 
	 * @param millis
	 *            the date to format expressed in milliseconds
	 * @param pattern
	 *            the pattern to use to format the date
	 * @param locale
	 *            the locale to use, may be <code>null</code>
	 * @return the formatted date
	 */
	public static String formatUTC(long millis, String pattern, Locale locale) {
		return format(new Date(millis), pattern, DateUtils.UTC_TIME_ZONE,
				locale);
	}

	/**
	 * <p>
	 * Formats a date/time into a specific pattern using the UTC time zone.
	 * </p>
	 * 
	 * @param date
	 *            the date to format
	 * @param pattern
	 *            the pattern to use to format the date
	 * @param locale
	 *            the locale to use, may be <code>null</code>
	 * @return the formatted date
	 */
	public static String formatUTC(Date date, String pattern, Locale locale) {
		return format(date, pattern, DateUtils.UTC_TIME_ZONE, locale);
	}

	/**
	 * <p>
	 * Formats a date/time into a specific pattern.
	 * </p>
	 * 
	 * @param millis
	 *            the date to format expressed in milliseconds
	 * @param pattern
	 *            the pattern to use to format the date
	 * @return the formatted date
	 */
	public static String format(long millis, String pattern) {
		return format(new Date(millis), pattern, null, null);
	}

	/**
	 * <p>
	 * Formats a date/time into a specific pattern.
	 * </p>
	 * 
	 * @param date
	 *            the date to format
	 * @param pattern
	 *            the pattern to use to format the date
	 * @return the formatted date
	 */
	public static String format(Date date, String pattern) {
		return format(date, pattern, null, null);
	}

	/**
	 * <p>
	 * Formats a calendar into a specific pattern.
	 * </p>
	 * 
	 * @param calendar
	 *            the calendar to format
	 * @param pattern
	 *            the pattern to use to format the calendar
	 * @return the formatted calendar
	 * @see FastDateFormat#format(Calendar)
	 * @since 2.4
	 */
	public static String format(Calendar calendar, String pattern) {
		return format(calendar, pattern, null, null);
	}

	/**
	 * <p>
	 * Formats a date/time into a specific pattern in a time zone.
	 * </p>
	 * 
	 * @param millis
	 *            the time expressed in milliseconds
	 * @param pattern
	 *            the pattern to use to format the date
	 * @param timeZone
	 *            the time zone to use, may be <code>null</code>
	 * @return the formatted date
	 */
	public static String format(long millis, String pattern, TimeZone timeZone) {
		return format(new Date(millis), pattern, timeZone, null);
	}

	/**
	 * <p>
	 * Formats a date/time into a specific pattern in a time zone.
	 * </p>
	 * 
	 * @param date
	 *            the date to format
	 * @param pattern
	 *            the pattern to use to format the date
	 * @param timeZone
	 *            the time zone to use, may be <code>null</code>
	 * @return the formatted date
	 */
	public static String format(Date date, String pattern, TimeZone timeZone) {
		return format(date, pattern, timeZone, null);
	}

	/**
	 * <p>
	 * Formats a calendar into a specific pattern in a time zone.
	 * </p>
	 * 
	 * @param calendar
	 *            the calendar to format
	 * @param pattern
	 *            the pattern to use to format the calendar
	 * @param timeZone
	 *            the time zone to use, may be <code>null</code>
	 * @return the formatted calendar
	 * @see FastDateFormat#format(Calendar)
	 * @since 2.4
	 */
	public static String format(Calendar calendar, String pattern,
			TimeZone timeZone) {
		return format(calendar, pattern, timeZone, null);
	}

	/**
	 * <p>
	 * Formats a date/time into a specific pattern in a locale.
	 * </p>
	 * 
	 * @param millis
	 *            the date to format expressed in milliseconds
	 * @param pattern
	 *            the pattern to use to format the date
	 * @param locale
	 *            the locale to use, may be <code>null</code>
	 * @return the formatted date
	 */
	public static String format(long millis, String pattern, Locale locale) {
		return format(new Date(millis), pattern, null, locale);
	}

	/**
	 * <p>
	 * Formats a date/time into a specific pattern in a locale.
	 * </p>
	 * 
	 * @param date
	 *            the date to format
	 * @param pattern
	 *            the pattern to use to format the date
	 * @param locale
	 *            the locale to use, may be <code>null</code>
	 * @return the formatted date
	 */
	public static String format(Date date, String pattern, Locale locale) {
		return format(date, pattern, null, locale);
	}

	/**
	 * <p>
	 * Formats a calendar into a specific pattern in a locale.
	 * </p>
	 * 
	 * @param calendar
	 *            the calendar to format
	 * @param pattern
	 *            the pattern to use to format the calendar
	 * @param locale
	 *            the locale to use, may be <code>null</code>
	 * @return the formatted calendar
	 * @see FastDateFormat#format(Calendar)
	 * @since 2.4
	 */
	public static String format(Calendar calendar, String pattern, Locale locale) {
		return format(calendar, pattern, null, locale);
	}

	/**
	 * <p>
	 * Formats a date/time into a specific pattern in a time zone and locale.
	 * </p>
	 * 
	 * @param millis
	 *            the date to format expressed in milliseconds
	 * @param pattern
	 *            the pattern to use to format the date
	 * @param timeZone
	 *            the time zone to use, may be <code>null</code>
	 * @param locale
	 *            the locale to use, may be <code>null</code>
	 * @return the formatted date
	 */
	public static String format(long millis, String pattern, TimeZone timeZone,
			Locale locale) {
		return format(new Date(millis), pattern, timeZone, locale);
	}

	/**
	 * <p>
	 * Formats a date/time into a specific pattern in a time zone and locale.
	 * </p>
	 * 
	 * @param date
	 *            the date to format
	 * @param pattern
	 *            the pattern to use to format the date
	 * @param timeZone
	 *            the time zone to use, may be <code>null</code>
	 * @param locale
	 *            the locale to use, may be <code>null</code>
	 * @return the formatted date
	 */
	public static String format(Date date, String pattern, TimeZone timeZone,
			Locale locale) {
		FastDateFormat df = FastDateFormat.getInstance(pattern, timeZone,
				locale);
		return df.format(date);
	}

	/**
	 * <p>
	 * Formats a calendar into a specific pattern in a time zone and locale.
	 * </p>
	 * 
	 * @param calendar
	 *            the calendar to format
	 * @param pattern
	 *            the pattern to use to format the calendar
	 * @param timeZone
	 *            the time zone to use, may be <code>null</code>
	 * @param locale
	 *            the locale to use, may be <code>null</code>
	 * @return the formatted calendar
	 * @see FastDateFormat#format(Calendar)
	 * @since 2.4
	 */
	public static String format(Calendar calendar, String pattern,
			TimeZone timeZone, Locale locale) {
		FastDateFormat df = FastDateFormat.getInstance(pattern, timeZone,
				locale);
		return df.format(calendar);
	}

}
